U.S. Pat. No. 3,516,679 describes a sealing arrangement that is composed of at least two radial shaft sealing rings and that has sealing lips extending in the same direction. However, this type of sealing arrangement allows a sealing action in only one axial direction.
U.S. Pat. No. 2,818,283 describes another possible arrangement of two radial shaft sealing rings where the sealing lips are oriented to axially oppose one another. The space formed between the two sealing lips is provided with a supply channel and is used for receiving a fluid. Since, in this case, the sealing lips are oriented away from the space to be actually sealed, such an arrangement is not suited for sealing two highly pressurized media, since, at a relatively high pressure, the sealing lips would lift off automatically from the shaft surface.
British Patent GB 1,117,672 also describes a seal combination where two axially side-by-side configured radial shaft sealing rings having oppositely directed sealing lips are used. Between the two sealing rings, a gap is formed via which it is possible to vent the space formed between the sealing lips. However, to connect two identically constructed shaft sealing rings in series, a considerable overall axial length is required, which, in many case, is not available. Moreover, the sealing rings must be assembled separately, one after another.
German Patent Application DE 192 22 850 A1 also discusses a sealing arrangement where two sealing rings of the same shape and size are joined together in one piece, positioning means being inserted between the sealing rings that retain the sealing rings in fixed relative positions, and which has connection means for joining the sealing rings together. This is a very costly design whose use only seems practical in special cases, at the very least due to the high costs.
European Patent Specification EP 1 557 596 B1 describes a very simple approach for a radial shaft seal for sealing two media, where the radial shaft sealing rings have an identical design and are able to fit into one another. In this case, on their surfaces that are directed toward one another, the radial shaft sealing rings are provided with axially oriented ring segments, which interlock by force- and/or form-locking when radial shaft sealing rings are installed. Together with the radial inner surfaces of the outer ring segments, the radial outer surfaces of the inner ring segments form a snap-fit connection. Free clearance spaces, which form a venting gap, exist between the sealing rings. In this context, the snap-fit connection is formed by a conical configuration of the outer, respectively inner surfaces.